The Eustachian tube (ET) is a potential communication between the middle ear (ME) and nasopharynx (NP). The lumen of the ET is usually closed but can be transiently opened by the activity of the paratubal muscles. It is known that the ET opening function (ETF) is impaired in patients presenting with otitis media with effusion (OME) and that constitutive ET dysfunction (ETD) can cause the persistence of the disease as a chronic condition. No standard medical therapy is effective in improving ETF or in resolving persistent OME long-term and the usual treatment is insertion of ventilation tubes (VTs) which bypasses the ET to maintain an open communication between the ME and environment. However, the functional half-life of a VT in adults is approximately 4-9 months and the disease often recurs when the VT is extruded or becomes non-functional. Recently, an alternative and perhaps more permanent surgical treatment for ETD, balloon dilation of the ET (BDET), has been described as being relatively easy to perform, safe and efficacious in resolving OME and is being actively promoted to practicing surgeons for adoption in their practices. However, the few clinical studies that evaluated the efficacy of the procedure included small sample sizes, a weak definition of cure and were not randomized, blinded or sham controlled. Importantly, none of the studies evaluated the direct effect of the procedure on ETF. Here, we propose to conduct a pilot study to define the safety and efficacy with respect to improving ETF of BDET. Over a 2-year period, we will identify otherwise healthy patients between 18-50 years of age who have VTs inserted as a treatment for OME caused by ETD. Forty of the patients who provide informed consent for experimental, unilateral BDET will be enrolled as subjects in the study. They will have baseline ETF tests and endoscopic ET/NP evaluations to document the presence or absence of ETD. The subset of subjects with ETD will be evaluated for 3 common conditions that can down-grade ETF: allergy, sinusitis and gastro-esophageal reflux disease. If a condition is diagnosed, the subject will be treated medically as appropriate; otherwise, they will be treated with intranasal steroids. ETF tests and nasal endoscopic examinations will be repeated and 20 subjects with ETD unresponsive to medical treatment will have unilateral BDET done under monitored anesthesia care. For safety and measurement of ET luminal geometry, a modified CT protocol focused on the ET and ME will be done prior to the procedure. ETF tests and endoscopic evaluations will be repeated at 1, 3 and 6 months and the CT scan will be repeated at 3 months after the BDET. The data will be analyzed to: define the frequency and cause of ETD in unselected adults with OME; determine if a short course of medical treatment for co-morbid conditions or for inflammation can be used to disqualify subjects from consideration for BDET, identify the type and frequency of complications associated with the procedure, describe the effect of the procedure on ETF and ET luminal geometry. These results will determine if a multi-center, phase II/III clinical trial ofthe procedure is warranted.